This invention relates to an airstream control system for a hovercraft, and more particularly to an airstream control system in which an impeller can be rotated from a position providing high lift to a position providing high thrust in addition to providing lift.
U.S. Pat. No. 3,827,527 (the ""527 patent), issued to William R. Bertelsen, one of the present inventors, describes a ground effect vehicle, commonly known as a hovercraft. The ""527 patent discloses an impeller mounted on a gimbal framework, which includes a generally horizontally positioned ring. The ring has a first axis passing from one point of the ring to a second point of the ring and in between which the impeller is rotatably mounted. The gimbal framework further includes a second axis, transverse to the first axis and passing from a third point of the ring to a fourth point of the ring. The third and fourth points of the ring are rotatably mounted to a stationery platform of the hovercraft.
The gimbal framework of the ""527 patent beneficially has allowed the impeller to be rotated to different positions to produce an airstream for lifting the hovercraft up above a surface such as land or water, and also to produce thrust to move the craft in a horizontal direction. More particularly, by being mounted in the gimbal framework, the impeller can be oriented to direct an airstream straight downwardly into a lift air chamber, for lifting the hovercraft. Considering the foregoing vertical orientation as 0 degrees, the impeller can be practically rotated up to an angle limited to about 30 degrees. This is due to the ring of the gimbal framework, which surrounds the impeller and abuts against structure forming an orifice to a lift air chamber beneath the impeller. Nevertheless, this arrangement beneficially allows a large degree of maneuverability of the hovercraft.
The present invention relates to further innovation to allow an impeller to extend its degree of rotational movement from having its airstream oriented at 0 degrees, or vertically downward into a lift chamber, to an angle that substantially exceeds 30 degrees and that may even reach 90 degrees. This would allow an impeller to provide a higher degree of thrust, permitting greater maneuverability of the hovercraft in terms of both direction and speed.
Three preferred aspects of the invention may be included in an airstream control system for a hovercraft that includes a platform and a lift gas chamber beneath the platform. According to a first preferred aspect, the system includes an impeller for receiving air at an inlet and discharging pressurized air at an outlet as an airstream. The impeller is positioned above an orifice of the lift gas chamber. The impeller is supported along a first axis transverse to the airstream and about which the impeller is rotatable by a first axis frame that is rotatable about a pair of first axis supports fixed to the platform. The impeller is further supported along a second axis transverse to the airstream and about which the impeller is rotatable by a second axis frame that is attached to the first axis frame and that comprises a first arm supporting a first point of the impeller and extending upstream of the impeller. A first channel arrangement fixed to the platform can receive the first arm of the second axis frame so as to allow a higher degree of tilting of a main axis of the impeller from vertically downward than in the absence of the first channel arrangement.
Beneficially, the foregoing aspect of the invention allows tilting of the impeller substantially more than in the above-mentioned prior art. In a preferred embodiment, the impeller can be titled up to 90 degrees from vertically downward for maximum thrust.
According to a second preferred aspect, the system may include an arrangement to substantially seal the orifice to the lift gas chamber downstream of the impeller from upward flow of air. According to a third preferred aspect, the system may include a stator positioned downstream of the impeller to prevent various airflow problems when the impeller is titled at 90 degrees from vertically downward.